Another tornado outbreak: When will it end? Is it unprecedented? Could it happen here?

Another day, another tornado outbreak. Yesterday the twisters tore through Oklahoma and Kansas, just two days after a massive tornado ripped through the southwest Missouri town of Joplin and killed 122 people. Also on Tuesday the National Oceanic and Atmospheric Administration bumped the Joplin tornado up to EF-5 status, the highest on the Enhanced Fujita scale.

This has proven to be a remarkable year for tornadoes based upon a preliminary count kept by the Storm Prediction Center:

The chart above shows this year’s count (black line), beginning in mid-April, surpassing all previous years in terms of a total count of tornadoes. Please note that this years “adjusted” numbers represents the best attempt of meteorologists to weed out over-counted twisters.

In answer to the question of when this violent tornado season is likely to end, the curves above begin to flatten by mid-July, so the Midwest can finally begin to breathe a bit easier in six or seven weeks.

The issue then becomes whether this year truly represents the beginning of something new, or if it’s just an anomalous year. The following chart shows the number of F3-F5 tornadoes, by year, since 1950. This is a better metric to use than total tornadoes, because many more F0 and F1 tornadoes are counted today because of factors such as population increase, increased tornado awareness, and more robust and advanced reporting networks.

(National Climatic Data Center)

From this chart, it doesn’t appear this year is unprecedented, and there appears to be no upward trends in U.S. tornado activity. Following this year’s remarkable April, NOAA has begun to assess whether this year’s activity may be attributable in some way to climate change. You can find its preliminary assessment here.

In summary, the report states:

Neither the time series of thermodynamic nor dynamic variables suggests the presence of a discernible trend during April; any small trend that may exist would be statistically insignificant relative to the intensity of yearly fluctuations. A change in the mean climate properties that are believed to be particularly relevant to major destructive tornado events has thus not been detected for April, at least during the last 30 years. So far, we have not been able to link any of the major causes of the tornado outbreak to global warming. Barring a detection of change, a claim of attribution (to human impacts) is thus problematic, although it does not exclude that a future change in such environmental conditions may occur as anthropogenic greenhouse gas forcing increases.

In other words, the current activity does not appear to be related to climate change, but it cannot be ruled out.

Finally, I wanted to present the following map, which shows the tracks of all F3 tornadoes since 1950. I think it’s an important graphic because it really shows how the concept of “tornado alley” is something of a misnomer. Large, violent tornadoes can and do occur across nearly all of the United States east of the Rocky Mountains.

(UNL)

Although infrequently, such events can and do affect Houston, most recently in 1992 with an outbreak of 17 tornadoes. The system included an F4 tornado, but most fortunately no one died.

66 Responses

With all the news stories about tornadoes this year, I was just wondering aloud to a co-worker if it was truly an exceptional year or just news coverage. I come to my favorite blog to find objective data regarding tornadoes as the latest entry. Great work!

Eric, the outbreak that hit Houston was in November of 1992. The F4 went through Channelview. I may be mistaken, but I don’t recall a 1994 outbreak. I remember the flood from that year though. In total, there were 6 tornadoes that moved through Houston that day—one very close to downtown.

Beyond the human suffering and material losses these storms are causing the next thing that comes to my mind is the insured cost of these kind of weather events and the fact that the computers at insurance companies must be running in high gear figuring out how to recoup the losses, and future projected losses as well, with increased premiums.

Could it happen here? It certainly is within the realm of possibility.

This is a fascinating and dangerous year.
The correlation between the rains passing to our north and east, followed by strong hot winds triggering tornados in about 24 hours seems very strong.
I look forward to what Dr. N-G has to say about this.

Terrible tornado in Joplin, and as a native Missourian it’s especially sad to see the tremendous loss of life. Still I have to wonder and be somewhat cynical when I ask if there was a political element in upgrading the intensity ranking of the Joplin storm from EF4 to EF5 ?

Not everything is political. It takes some time to assess the damage reports and the weather data. It is very common for a preliminary estimate or designation to be made and then later revised upward, or down.

Don, I highly doubt this upgrading has anything to do with politics. When I first saw the damage I told my wife that had to be an EF5. I’m not an expert but growing up I tried to get my hands on every book about weather and tornadoes in the public library. And I’ve learned many things reading about tornadoes throughout history. I do believe the Tri-State tornado of 1925 is still the single most deadly tornado in our history. But I’m afraid the majority of these 1500 so called “missing” might end up being fatalities – I hope not. If so, it will surpass that tornado as most deadliest.

It appears that the strong violent tornadoes are just hitting major urban centers this season. Take the same tornado and put it in an open field and it just becomes great video for the storm chasers and causes little to no damage and no loss of life.

last year I witnessed a small tornado at the intersection of Washington and Studewood. The news reported it as a micro-burst, but I was stopped at the light and saw the funnel form and come down on a couple of buildings on Center St, ripping off roofing and tiles. It dissipated quickly, maybe within 1 minute of forming.

I have to wonder if the Texas drought and the concentration of tornadoes in the mid-section of the country are related in a big picture, La Nina kind of way. Wouldn’t these fronts normally come down to the Gulf and spread out over a larger portion of the southern US?

I’ve thought the same thing related to the drought here and the flooding in the Mississippi River watershed, and it could be possible that these storms with tornados have similar causes of being concentrated and unable to move as they normally do over a larger area. One way to check would be to look at past La Nina years to see about drought/flood and tornado frequency in those years. It may not be an exact correlation, but it might be part of the cause when coupled with other factors.

What I find interesting is the effect of that two day major outbreak on the total numbers. Without it, the black line is much closer to the median. It may just be an anomolous few days that skew the numbers for the year.

Also, by definition, any tornado that only goes through unoccupied fields or pastures is considered an EF-0 tornado, even if it has measured 300+mph peak winds. Since the scale is based on damage, the numbers may have to adjusted for the area covered by suburbanization and the changing methods of construction.

Eric I would say that if you take the tornado data from 1950 on and you looked at each state that a tornado is reported in each year you would find “tornado ally” has more relevance. Good to see that a perceived spike in activity is just that and that at least for now there is no connecting to the bigger concern around global warming.

“In other words, the current activity does not appear to be related to climate change, but it cannot be ruled out.” Good article until you had to throw this line into print. Of course it cannot be ruled out and neither can the correlation with toilet paper purchases be ruled out using the same logic.

It seems that this is an active tornado year because of La Nina, and a lot of bad luck for the tornadoes to be hitting population centers.

I read on the Houston NWS site that May is going to be the 4th month in a row with less than an inch of rain in Houston. They said that three months in a row of less than in inch had never happened before at the official observation site. I wonder if the drought severity could be related to global warming, but I doubt the tornado severity this year is related.

Why would you doubt that? The National Academy predicted more severe weather. All weather. Here is my theory. you heat water from the bottom, convection causes the water to heat evenly other wise only the bottom of the water would heat. Same thing with the air. The air is churning more violently. Hopefully this is working out and releasing the energy, otherwise I think a store of the extra energy (heat) would be stored where?

I haven’t read much about the experts predictions on tornado frequency/intensity related to global warming. I did read something about global warming and hurricane intensity in this year’s Colorado State hurricane prediction. They didn’t believe that hurricanes should get more intense in a warming world. It was complicated but if I remember correctly, the intensity of hurricanes depends on the temperature difference across the atmospheric column. In global warming all the layers of the atmosphere warm, so the temperature difference across the vertical column is not increased; therefore, the hurricane intensity is not increased. Something like that. Anyway, it is complicated but interesting to weather geeks.

You anticipate me. I am actually in the process of gathering some data to determine how windy it actually has been this spring, how above normal the winds have been, and why. I hope to have something within the next several days.

they just HAD to say “‘anthropogenic’ greenhouse gas forcing” didn’t they? In fact, the previous 2 sentences which were very clear in distancing this from AGW; then they throw this red herring on the table. Instead of building concensus, they just trashed the opportunity to actually have folks prepare for inevitable climate change by giving the extremists on BOTH sides more ammunition. Leave that 1 single word out and no one one either side could pick it apart. Leave it in and you might as well have Jim “gimmethegrant” Hansen in the byline.

The Weather Channel last night had a very good segement on regarding the large number of strong tornadoes that have occured in the U.S. this year, and there take was they were attributable to the cooler waters of the Pacific producing upper level lows that have collided with stalled warm fronts and the hot air of the Gulf.

Why is it the climate change deniers always have to object to any mention of anthropogenic climate change? They can choose to live with their heads buried in the sand if they wish, but most of us want to know the science of any weather phenomena, so we are willing to consider all possibilities. This article is a fair treatment of the subject. It just galls the deniers that Eric Berger concludes, as the overwhelming majority of scientists do, that anthropogenic global warming is occurring. Since the minds of the deniers are already made up, why even consider other possibilities, since their lives are based on their beliefs and not on scientific evidence?

Lizard,
Perhaps a better question would be to ask why AGW believers confuse weather events with climate catastrophes?
Do you not understand terms like ‘history’ and ‘climate’ vs. ‘weather’?
Despite >22 years of calls for CO2 caused climate doom, not one weather event, or pattern of weather events in this period of time, have been historically unprecedented.
Claiming this year’s tornado season is connected to or caused by AGW is like claiming that aliens are under your bed waiting to abduct you if you fall asleep.

November 21, 1992 was the outbreak in Houston. I was in renting a home in Channelview, our garage was removed from our home, with part of the roof, but the homes right behind me were swept off their foundations. I remember walking out of my house and seeing the destruction and telling my wife “there’s got to be some dead people back there”, but fortunately, as Eric said, and miraculously, there were no deaths, even though it happened at about 3 pm on a Saturday afternoon when plenty of people should have been home.

March 18, 1925. The Tornado. More than a mile wide at times, howled across three states, MO, IL, & IN in 3 1/2 hours, leaving 219 miles of destruction and 695 bodies in its wake.

More than 800 people died in an 1884 tornado outbreak, but that storm involved a cluster of tornadoes in several states. A 1974 cluster killed more than 300 people in 13 states.

My friend’s mother lived through Illinois’ 3rd deadliest tornado disaster on record which occurred on May 26, 1917. On that date, 101 people were killed across central Illinois, most of them in the Mattoon/Charleston area. Injuries totaled approximately 638.
Originally, this was believed to be a single tornado with a path 293 miles long, extending from the Mississippi River across from Louisiana, MO, all the way across central portions of Illinois and Indiana, ending near Mount Vernon, IN, over a total time span of 7 hours 20 minutes. This was later determined to be 4 to 8 separate tornadoes; the Illinois portion was approximately 155 miles (including times it was aloft), over a time of approximately 4 hours. The strongest part of the tornado, through Mattoon/Charleston, was later determined to be F4 intensity on the original Fujita scale.

Don’t really believe the current tornado outbreak could be called unprecedented. This is a violent earth.

Thanks Donna,
These long walker tornados are curious and dangerous phenomena. They seem to like the states above Missouri the most.

And thanks Eric,
For the map. Looks like tornados are less likely in mountains and dry places. Even though I have known people in some of those dry places. They say they saw tornados in those counties in that 50 year period.

Eric -
I guess it was not Houston proper – but in February 1998, a tornado hit First Colony Mall and the nearby ice skating rink. It tore the outer wall off of Dillard’s and damaged the JC Penney’s. We were driving back from Galveston and saw it dip down from a distance. Pretty hairy.

I’ve never been through a tornado and never want to; it’s one of my biggest fears. I’d much rather have hurricanes. At least we see them coming and know what we’re getting into. Even the worst hurricane doesn’t have to result in much loss of life, either, if people in Katy evacuate in time and the rest of us hunker down.

This year’s tornado outbreak is most certainly linked to climate change, but not in the way many of you would like to believe. The Earth’s climate is beginning to cool, and it is the battle between warm and cold that causes tornados. The average global temperature in the upper levels of the atmosphere (25,000 ft) is much colder than last year, and in fact is the coldest on record since accurate satellite measurements began in the early 90′s. Go ahead and worry about climate change, but worry that it is going to get colder, not warmer. The greatest advances in civilation have all occurred during warm periods, while the greatest famines have occurred during cool cycles.

Right on. But the warm earth crazies don’t read history. The Year Without a Summer (also known as the Poverty Year, Year There Was No Summer, and Eighteen Hundred and Froze to Death[1]) was 1816, in which severe summer climate abnormalities caused average global temperatures to decrease by about 0.4–0.7 °C (0.7–1.3 °F),[2] resulting in major food shortages across the Northern Hemisphere. And look how big everything grew during the age of the dinosaures. Warmer is better.

Very scary stuff to see. Seems like things are getting more frequent and more intense. I’m almost afraid to even consider what our hurricane season will be like this year, especially with the tornadic craziness abound!

I would say we need the Army Corps to level the rockies, that will probably help, looks like they form when the air comes over the mts onto the plains. New WPA project. We could use the fill to fill all those pesky wetlands and get rid of mosquitoes and alligators.

In reality, it appears that the 1950 to present graph shows an inverse correlation to global temperature. There was a trend towards increasing tornadoes until the mid ’70s (global cooling), then a decreasing trend to present day (global warming) with this year being another anomaly on the graph.

I grew up in Oklahoma and still have alot of family that still lives there. One of the tornadoes yesterday hit the east side of my hometown, and also hit my old Highschool. Luckily all my family is okay. In 2003 I was in the GM plant in Oklahoma City when it got hit by an EF4 tornado. I know we hear of alot of deaths associated with these storms, but the deaths are quite low considering what they would be without any warning systems like tornado sirens, tv or radio. At the GM plant we had about a 10 to 15 minute warning, and we all got down in the train tunnel and took cover. 1500 employees were in the plant and no one was killed. Oklahomans know and expect these storms every spring. And almost every Oklahoma knows what to do and where to hide to give yourself the best chance for survival too. I’m a bit of a weather nerd, and man I miss living in Oklahoma. This boring Houston weather is getting very boring. It doesn’t even rain anymore!

Thanks Eric! That graph is very interesting. I see where around 1950 is when the deaths starting to trend downward. I would have to imagine television played a major role in that. My grandpa tells me that growing up out on the farm with no electricity, they would see some storms blowing in and they would just hide near a creek bottom or ditch somewhere and just take cover as best they could. We have RADAR now, my grandpa said back then they used their EYE-DAR.

True the level of distruction is hard to take in but considering what it was subjected to the basic concrete structure of that hospital seems to have faired pretty well. Stronger wall sections between the main structural members and less glass would probably have helped. Designing anything to withstand over 200 mph winds could become pretty costly though. I wonder if Kansas, Oklahoma and Missouri have windstorm coverage programs like Texas has?

two things
according to the chart, the biggest surge of tornado’s was in the 70′s when all the famous meteorologist, broadcast media and print media [basically the same people today] blamed it on global cooling. maybe, just maybe us ignorant non believers in MAN MADE global warming don’t wear blinders and actually question those social scientists paid with government grants to come to the “right conclusion”.

point number two.
as stated by one of your weatherman yesterday on the weather channel “the tornadoes are not unusual, they are just hitting populated areas this year”